NASA’s cost assessments for the Space Launch System (SLS) are sound enough for near-term planning purposes but unsuitable for developing a baseline estimate for the congressionally mandated heavy-lift rocket, according to a review of the agency’s plans conducted by consulting firm Booz Allen Hamilton.

“NASA should treat the estimates as serviceable point estimates for budget planning in the near-term 3-5 year budget horizon as they represent the basis upon which future estimates can be constructed,” Booz Allen Hamilton wrote in the conclusion appended to a summary of the report.

However, the consulting firm warned that “due to procurement of items still in development and large cost risks in the out years, NASA cannot have full confidence in the estimates for long-term planning.”

NASA Administrator Charles Bolden told the House Science Committee last month that NASA would make no move to proceed with SLS development until and unless the Booz Allen Hamilton report affirmed the soundness of the agency’s cost projections.

At press time, NASA had not announced a final SLS design.

Only the summary of Booz Allen Hamilton’s report has been released to the public. NASA released that document late Aug. 19. It includes no cost figures. The report was not an outside assessment of the probable costs of SLS and its companion crew and ground systems. Rather, the McLean, Va.-based firm parsed NASA’s own cost estimates for the projects to ensure that they complied with federally prescribed practices.

Besides SLS, Booz Allen Hamilton’s report reviewed NASA’s internal cost estimates for two other programs: the Multi-Purpose Crew Vehicle (MPCV) that would launch atop SLS, and the 21st Century Ground Systems Programs. The latter is an initiative to upgrade NASA’s launch and ground-support infrastructure in the post-shuttle era. The ground systems program includes a mobile launch platform built for the canceled Ares 1 rocket.

The release of the Booz Allen Hamilton report prompted one lawmaker to again call on NASA to start work on SLS.

“This additional independent cost assessment confirms what NASA officials have known for months: The NASA approach to human space flight is sound, achievable, and can be initiated within our currently constrained fiscal limitations,” Sen. Kay Bailey Hutchison (R-Texas) said in an Aug. 24 press release. “We strongly encourage NASA to immediately announce this week — not next month — the design for their next launch vehicle, which will halt the further loss of skilled aerospace workers now poised to be laid off from the NASA manned spaceflight program.”

Hutchison, looking out for the interests of the Johnson Space Center in Houston, has been a staunch advocate of SLS. She is the ranking member of the Senate Commerce, Justice, Science Committee, which wrote SLS into law.

The Space Launch System conceived by NASA and being vetted by the White House Office of Management and Budget is nearly identical to the Ares 5 heavy-lifter concept from the Constellation program. SLS and MPCV are intended primarily for crewed exploration missions to deep space. The SLS design sent to the White House includes a liquid hydrogen-fueled core stage powered by space shuttle main engines, an Apollo-derived J-2X upper stage, and side-mounted solid-rocket boosters derived from the space shuttle and Constellation programs. Following initial test flights, the solid boosters could be replaced by liquid boosters in a planned competitive procurement.

Bolden has said SLS would not be ready to fly its first uncrewed test until 2017.